Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
hieu van » hieu va, thien van, lieu va
su triet » su viet, su tien, ve triet
cam duc » cam xuc, cao duc, pham duc
sach ky » sac ky, sach y, sach ty
hanh de » hanh ve, hanh kem
hang di » hang doi, hang vi, hang dien
van cam » van nam, van lam, van cau
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuat sach ky nang ((o hoi) OR (o hoc)). hieu van cam duc va ((hanh de) or (hang di)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach ky nang ((o hoi) OR (o hoc)). hieu van cam duc va ((hanh de) OR (hang di)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach ky nang ((o hoi) OR (o hoc)). hieu van cam duc va ((hanh de) or (hang di)) su triet".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky nang ((o hoi) OR (o hoc)). hieu van cam duc va ((hanh de) or (hang di)) su triet*.